With this in mind, a team of US scientists has analysed the net effect on climate of regulating emissions from individual economic sectors. Cleaning up the air by removing certain aerosol-forming chemicals, for example, could actually increase warming in the short-term.
"Each economic sector emits a unique portfolio of gases and aerosols that affect the climate in different ways and on different timescales," Nadine Unger of NASA Goddard Institute for Space Studies and Columbia University, both in the US, told environmentalresearchweb. "It is likely the net effect of aerosol particulate pollution is masking about 50% of the global warming due to greenhouse-gas emissions since the industrial revolution."
While it's important to reduce aerosol air pollution to protect human and ecosystem health, Unger says that we need to be extremely careful about how that aerosol pollution mask is removed, to avoid accelerating global warming or potentially pushing the Earth's climate system past a tipping element.
Unger and colleagues from NASA Goddard Institute for Space Studies; Columbia University; University of Illinois; Urbana-Champaign; Environmental Defense Fund and Lawrence Berkeley National Laboratory, US, believe that their analysis identifies the most effective opportunities for fast mitigation of climate change.
"If the policy goal is to achieve rapid and immediate reduction in human-made climate forcing, then effective opportunities lie in reducing emissions from the on-road transportation, household biofuel and animal husbandry sectors," said Unger. Reducing emissions from the on-road transportation sector is particularly attractive because this action yields both rapid and longer-term climate benefits.
Protecting Earth's climate in the longer term will also need reductions of emissions from the power and industry sectors, in addition to on-road transportation, say the researchers.
"The decadal-scale climate effects of cooling aerosols need to be included in evaluations of control strategies, especially for actions that affect the power, industry, biomass burning and shipping sectors," added Unger.
The researchers aimed to provide climate impact information in a way that would be more helpful for policy makers, helping them to produce "smart climate policy that avoids unintended consequences".
To date the scientists have focused on global climate but in the future they plan to assess regional climate impacts, as well as exploring the effects of climate change on water supply and land ecosystems.
Unger says there are also plans to investigate many of the sectors in even greater detail. "In the power sector, for example, we might look specifically at power stations that operate with coal or natural gas," she said. "And in the on-road transportation sector, we might break out heavy from light duty vehicles."
Finally the researchers plan to partner with environmental economists to determine the damage costs of emissions from all the sectors due to both climate and air quality impacts. They can then use these results to develop alternative mitigation scenarios.
"There are large uncertainties associated with the aerosol pollution effects on climate, especially related to how the aerosols affect clouds," said Unger. "Therefore, we emphasize the need for a multi-model-based assessment of the net climate impacts of key economic sectors and anticipate with optimism that such an effort can be organized in the near future."
The researchers reported their work in PNAS.